SEMOIS (also spelt Semoy and Semoys), a river of less than 120 m. in length rising near Arlon in Belgium, and flowing into the Meuse near Monthermé in France. It is Belgian for about 100 m. and French for the remainder, entering France a short distance west of the village of Bohan. It passes through the most picturesque scenery in Belgium and is remarkable for its sinuous course, its length of 120 m. representing only 47 in a straight line. Bouillon is the only town on its banks, and since it is not navigable it has escaped the contamination of manufacturing life; its valley remains an ideal specimen of sylvan scenery and medieval tranquillity.